Ranking of Acids and Bases, the pKa Chart

2 RANKING OF ACIDS AND BASES, THE pKa CHART 3.2.1 The pK a Chart and pH Relationships 

Because the pATg chart is a composite of many experimental observations under widely different conditions, it has the greatest extrapolation errors at its extremes and is most accurate in the center, between -2 and 16. While we will write for simplicity HA ionizing to give H + A , it is always true that the proton is transferred to a base. For our pATa chart (in the Appendix) this base is assumed to be water. 

Answer pH 7.2 is at p/fa2 equal concentrations of H2P04 and HP04 are needed. At pH of 8.2, one unit more basic, 10 times more conjugate base HP04 than conjugate acid H2P04 is needed to get the correct pH. For any mixture of an acid and its conjugate base, the pH will be within a few pH units of the pATa of the acid used. 

The old phrase a snowball s chance in hell illustrates the fact that the environment can play a critical part in the probability of existence of any species. Since = 

Acidic media contain powerful electrophiles and rather weak nucleophiles, whereas basic media contain excellent nucleophiles and weak electrophiles. Similarly, no medium can possibly be both strongly acidic and strongly basic. 

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